Fundamental study of small interfering RNAs for ganglioside GD3 synthase gene as a therapeutic target of lung cancers

Identifying an Immune-Related Gene ST8SIA1 as a Novel Target in Patients With Clear-Cell Renal Cell Carcinoma

Clear-cell renal cell carcinoma (ccRCC) is one of the most common urological cancers. The tumor microenvironment plays an important role in tumor development. The present study was conducted to identify novel immune-related biomarkers. The differentially expressed genes were identified using the ESTIMATE algorithm base on GEO and TCGA databases. The Kaplan–Meier survival curve and univariate and multivariate analyses were performed. The association between ST8SIA1 and the immune system was explored. The gene set enrichment analysis (GSEA) and online databases were used for functional annotation. ST8SIA1 was identified as a potential prognostic gene. Elevated ST8SIA1 was observed in the tumor tissues compared with adjacent normal tissues and associated with higher T stage and advanced TNM stage (all p < 0.05). The mRNA and protein levels of ST8SIA1 in cancer tissues and cells are also upregulated. The Kaplan–Meier survival curve and univariate and multivariate analyses showed that higher expression of ST8SIA1 was associated with worse OS (all p < 0.05). ST8SIA1 expression levels were negatively correlated with tumor purity and positively associated with infiltrated immune cells and expression of immune checkpoint genes. Function analysis also revealed that ST8SIA1 was significantly associated with immune-related pathways. In conclusion, ST8SIA1 was identified as an immune-related gene and a potential target in ccRCC patients. Further relevant studies are required to validate our findings.

A2B5 Expression in Central Nervous System and Gliomas

A2B5 IgM recognizes c-series gangliosides with three sialic acids. The aim of this review was to focus on A2B5 expression in the central nervous system and gliomas. In brain development, A2B5+ cells are recorded in areas containing multipotent neural stem cells (NSC). In adults, A2B5+ cells persist in neurogenic areas and in white matter where it identifies oligodendrocyte precursor cells (OPCs) but also cells with NSC properties. Although the expression of A2B5 has been widely studied in culture, where it characterizes bipotential glial progenitor cells, its expression in vivo is less characterized mainly because of technical issues. A new interest was given to the NSCs and OPCs since the discovery of cancer stem cells (CSC) in gliomas. Among other cell surface molecules, A2B5 has been identified as an accurate marker to identify glioma CSCs. We and others have shown that all types of gliomas express A2B5, and that only A2B5+ cells, and not A2B5- cells, can generate a tumor after orthotopic implantation in immunocompromised animals. Moreover, A2B5 epitope expression is positively correlated with stemness and tumor growth. This review highlights that A2B5 is an attractive target to tackle glioma CSCs, and a better characterization of its expression in the developing and adult CNS will benefit to a better understanding of gliomagenesis.

Signaling domains of cancer-associated glycolipids

Immunotherapy of malignant cancers is now becoming one of representative approaches to overcome cancers. To construct strategies for immunotherapy, presence of tumor-specific antigens should be a major promise. A number of cancer specific- or cancer-associated antigens have been reported based on various experimental sets and various animal systems. The most reasonable strategy to define tumor-specific antigens might be "autologous typing" performed by Old's group, proposing three classes of tumor-antigens recognized by host immune systems of cancer patients. Namely, class 1, individual antigens that is present only in the patient's sample analyzed; class 2, shared antigens that can be found only in some group of cancers in some patients, but not in normal cells and tissues; class 3, universal antigens that are present in some cancers but also in normal cells and tissues with different densities. Sen Hakomori reported there were novel carbohydrates in cancers that could not be detected in normal cells mainly by biochemical approaches. Consequently, many of class 2 cancer-specific antigens have been revealed to be carbohydrate antigens, and been used for cancer diagnosis and treatment. Not only as cancer markers, but roles of those cancer-associated carbohydrates have also been recognized as functional molecules in cancer cells. In particular, roles of complex carbohydrates in the regulation of cell signaling on the cell surface microdomains, glycolipid-enriched microdomain (GEM)/rafts have been reported by Hakomori and many other researchers including us. The processes and present status of these studies on cancer-associated glycolipids were summarized.

Sphingolipid metabolism in the development and progression of cancer: one cancer's help is another's hindrance

Cancer development is a multistep process in which cells must overcome a series of obstacles before they can become fully developed tumors. First, cells must develop the ability to proliferate unchecked. Once this is accomplished, they must be able to invade the neighboring tissue, as well as provide themselves with oxygen and nutrients. Finally, they must acquire the ability to detach from the newly formed mass in order to spread to other tissues, all the while evading an immune system that is primed for their destruction. Furthermore, increased levels of inflammation have been shown to be linked to the development of cancer, with sites of chronic inflammation being a common component of tumorigenic microenvironments. In this Review, we give an overview of the impact of sphingolipid metabolism in cancers, from initiation to metastatic dissemination, as well as discussing immune responses and resistance to treatments. We explore how sphingolipids can either help or hinder the progression of cells from a healthy phenotype to a cancerous one.

Cancer-Associated Glycosphingolipids as Tumor Markers and Targets for Cancer Immunotherapy

Aberrant expression of glycosphingolipids is a hallmark of cancer cells and is associated with their malignant properties. Disialylated gangliosides GD2 and GD3 are considered as markers of neuroectoderm origin in tumors, whereas fucosyl-GM1 is expressed in very few normal tissues but overexpressed in a variety of cancers, especially in small cell lung carcinoma. These gangliosides are absent in most normal adult tissues, making them targets of interest in immuno-oncology. Passive and active immunotherapy strategies have been developed, and have shown promising results in clinical trials. In this review, we summarized the current knowledge on GD2, GD3, and fucosyl-GM1 expression in health and cancer, their biosynthesis pathways in the Golgi apparatus, and their biological roles. We described how their overexpression can affect intracellular signaling pathways, increasing the malignant phenotypes of cancer cells, including their metastatic potential and invasiveness. Finally, the different strategies used to target these tumor-associated gangliosides for immunotherapy were discussed, including the use and development of monoclonal antibodies, vaccines, immune system modulators, and immune effector-cell therapy, with a special focus on adoptive cellular therapy with T cells engineered to express chimeric antigen receptors.

Epigenetic hypomethylation and upregulation of GD3s in triple negative breast cancer

Background

Breast cancer remains a major health problem in the world. Triple-negative breast cancer (TNBC) is an aggressive subtype with very poor prognosis. Up to now, the mechanism behind TNBC's activity is still unclear and no candidate drug target has been identified. Thus, it is of critical importance to elucidate the pathways in TNBC and identify the relevant biomarkers. Recent studies showed that ganglioside D3 synthase (GD3s) played a very important role in development of cancers. However, the physiological functions and associated pathways of GD3s in TNBC are still unclear.

Methods

In silico analysis of the expression of GD3s in TNBC was conducted using The Cancer Genome Atlas (TCGA) and Oncomine databases. The proliferation of breast cancer cells was measured by MTT assay, colony formation by the soft agar method, and migration and invasion using Boyden chamber inserts. The methylation level of the gene encoding GD3s, ST8SIA1, in specimens was assessed by qMS-PCR and in silico using the UCSC gene browser. Protein expression was examined via immunohistochemistry (IHC), qRT-PCR and Western immunoblotting.

Results

In silico analysis showed a higher GD3s expression in ER^- than ER⁺ breast cancers and GD3s was also highly expressed in TNBC compared to other types of breast cancers. The elevated GD3s expression in TNBC cells and tissues was associated with hypomethylation of the ST8SIA1 gene. Overexpression of GD3s in human breast cancer cells increased their proliferation, migration, invasion and colony formation ability. GD3s expression in breast cancers was closely associated with relapse-free survival (RFS) and overall survival (OS).

Conclusions

In summary, these results suggest that GD3s may be a potential biomarker and drug target in treatment of TNBC.

Ganglioside GD3 synthase (GD3S), a novel cancer drug target

Gangliosides are a class of important glycosphingolipids containing sialic acid that are widely distributed on the outer surface of cells and are abundantly distributed in brain tissue. Disialoganglioside with three glycosyl groups (GD3) and disialoganglioside with two glycosyl groups (GD2) are markedly increased in pathological conditions such as cancers and neurodegenerative diseases. GD3 and GD2 were found to play important roles in cancers by mediating cell proliferation, migration, invasion, adhesion, angiogenesis and in preventing immunosuppression of tumors. GD3 synthase (GD3S) is the regulatory enzyme of GD3 and GD2 synthesis, and is important in tumorigenesis and the development of cancers. The study of GD3S as a drug target may be of great significance for the discovery of new drugs for cancer treatment. This review will describe the gangliosides and their roles in physiological and pathological conditions; the roles of GD3 and GD2 in cancers; the expression, functions and mechanisms of GD3S, and its potential as a drug target in cancers.

MicroRNA-33a and let-7e inhibit human colorectal cancer progression by targeting ST8SIA1

Colorectal cancer (CRC) is one of the leading causes of cancer mortality worldwide. Aberrant sialylation is crucially involved in the progression of various types of cancer. MicroRNAs (miRNAs) have been broadly studied in cancer. MicroRNA-33a (miR-33a) and Has-let-7e (let-7e) are non-coding RNA that can reduce cell motility and viability in cancer. In this study, miR-33a and let-7e levels were confirmed to be significantly down-regulated in CRC samples (n=32) and drug resistant cell line (HCT-8/5-FU) compared with those in the matched adjacent tissues and drug sensitivity cell line (HCT-8). ST8SIA1 was highly expressed in CRC tissues and HCT-8/5-FU cells, which was negatively correlated with miR-33a/let-7e expression. Luciferase reporter assays confirmed that both miR-33a and let-7e bound to the 3'-untranslated (3'-UTR) region of ST8SIA1. Inhibiting miR-33a/let-7e expression in CRC cells increased endogenous ST8SIA1 mRNA and protein levels. MiR-33a/let-7e knockdown promoted chemoresistance, proliferation, invasion, angiogenesis in vitro, and tumor growth in vivo. Whereas, ectopic expression of miR-33a/let-7e suppressed chemoresistance, proliferation, invasion and angiogenesis in CRC cell lines. ST8SIA1 knockdown mimicked the tumor suppressive effect of miR-33a/let-7e on CRC cells, while restoration of ST8SIA1 abolished the tumor suppressive effect of miR-33a/let-7e on CRC cells. Taken together, altered expression of miR-33a/let-7e was correlated with ST8SIA1 level, which might contribute to CRC progression. The miR-33a/let-7e-ST8SIA1 axis could be a therapeutic target for CRC patients.

Gangliosides: Structures, Biosynthesis, Analysis, and Roles in Cancer

Gangliosides are acidic glycosphingolipids containing one or more sialic acid residues. They are essential compounds at the outer leaflet of the plasma membrane, where they interact with phospholipids, cholesterol, and transmembrane proteins, forming lipid rafts. They are involved in cell adhesion, proliferation, and recognition processes, as well as in the modulation of signal transduction pathways. These functions are mainly governed by the glycan moiety, and changes in the structures of gangliosides occur under pathological conditions, particularly in neuro-ectoderm-derived cancers. With the progress in mass spectrometry analysis of gangliosides, their role in cancer progression can be now investigated in more detail. In this review we summarize the current knowledge on the biosynthesis of gangliosides and their role in cancers, together with the recent development of cancer immunotherapy targeting gangliosides.

Identification and Tumour-Binding Properties of a Peptide with High Affinity to the Disialoganglioside GD2

Neuroectodermal tumours are characterized by aberrant processing of disialogangliosides concomitant with high expression of GD2 or GD3 on cell surfaces. Antibodies targeting GD2 are already in clinical use for therapy of neuroblastoma, a solid tumour of early childhood. Here, we set out to identify peptides with high affinity to human disialoganglioside GD2. To this end, we performed a combined in vivo and in vitro screen using a recombinant phage displayed peptide library. We isolated a phage displaying the peptide sequence WHWRLPS that specifically binds to the human disialoganglioside GD2. Binding specificity was confirmed by mutational scanning and by comparative analyses using structurally related disialogangliosides. In vivo, significant enrichment of phage binding to xenografts of human neuroblastoma cells in mice was observed. Tumour-specific phage accumulation could be blocked by intravenous coinjection of the corresponding peptide. Comparative pharmacokinetic analyses revealed higher specific accumulation of 68Ga-labelled GD2-binding peptide compared to 111In-labelled peptide in xenografts of human neuroblastoma. In contrast to 124I-MIBG, which is currently evaluated as a neuroblastoma marker in PET/CT, 68Ga-labelled GD2-specific peptide spared the thyroid but was enriched in the kidneys, which could be partially blocked by infusion of amino acids.In summary, we here report on a novel tumour-homing peptide that specifically binds to the disialoganglioside GD2, accumulates in xenografts of neuroblastoma cells in mice and bears the potential for tumour detection using PET/CT. Thus, this peptide may serve as a new scaffold for diagnosing GD2-positive tumours of neuroectodermal origin.

Sialylation: an Avenue to Target Cancer Cells

Tumorigenesis and metastasis are frequently associated with altered structure and expression of oligosaccharides on cell surface glycoproteins and glycolipids. The expression of sialylated glycoconjugates has been shown to change during development, differentiation, disease and oncogenic transformation. Abnormal sialylation in cancer cell is a distinctive feature associated with malignant properties including invasiveness and metastatic potential. The alterations in sialylation is accompanied by changes in sialic acid, sialidase activity, sialyltransferase (ST) activity or sialoproteins. The present review summarizes the reports on alterations of sialic acid, linkage specific STs and sialoproteins, sialidase activity together with different subtypes of ST and sialidases mRNA expressions in various cancers like lung, breast, oral, cervical, ovarian, pancreatic etc. Sialic acids are widely distributed in nature as terminal sugars of oligosaccharides attached to proteins or lipids. The increase shedding of sialic acid observed in malignant tumors may be due to different types of sialidases. The amount of sialic acid is governed by levels of sialidases and STs. Various types of STs are also involved in formation of different types sialylated tumor associated carbohydrate antigens which plays important role in metastasis. The alterations associated with sialylation aids in early diagnosis, prognosis and post treatment monitoring in various cancers. Recently newer drugs targeting different interplays of sialylation have been developed, which might have profound effect in inhibiting sialylation and thus cancer metastasis and infiltration.

Centrosomal nucleolin is required for microtubule network organization

Nucleolin is a pleiotropic protein involved in a variety of cellular processes. Although multipolar spindle formation has been observed after nucleolin depletion, the roles of nucleolin in centrosome regulation and functions have not been addressed. Here we report using immunofluorescence and biochemically purified centrosomes that nucleolin co-localized only with one of the centrioles during interphase which was further identified as the mature centriole. Upon nucleolin depletion, cells exhibited an amplification of immature centriole markers surrounded by irregular pericentrin staining; these structures were exempt from maturation markers and unable to nucleate microtubules. Furthermore, the microtubule network was disorganized in these cells, exhibiting frequent non-centrosomal microtubules. At the mature centriole a reduced kinetics in the centrosomal microtubule nucleation phase was observed in live silenced cells, as well as a perturbation of microtubule anchoring. Immunoprecipitation experiments showed that nucleolin belongs to protein complexes containing 2 key centrosomal proteins, γ-tubulin and ninein, involved in microtubule nucleation and anchoring steps. Altogether, our study uncovered a new role for nucleolin in restricting microtubule nucleation and anchoring at centrosomes in interphase cells.

Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance

Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolipids have been well documented. Sphingolipids are known to play many structural and signalling roles in cells, as they are involved in the control of growth, survival, adhesion, and motility. In particular, in order to increase survival, cancer cells: (a) counteract the accumulation of ceramide that is endowed with pro-apoptotic potential and is induced by many drugs; (b) increase the synthesis of sphingosine-1-phosphate and glucosylceramide that are pro-survivals signals; (c) modify the synthesis and the metabolism of complex glycosphingolipids, particularly increasing the levels of modified species of gangliosides such as 9-O acetylated GD3 (αNeu5Ac(2-8)αNeu5Ac(2-3)βGal(1-4)βGlc(1-1)Cer) or N-glycolyl GM3 (αNeu5Ac (2-3)βGal(1-4)βGlc(1-1)Cer) and de-N-acetyl GM3 (NeuNH(2)βGal(1-4)βGlc(1-1)Cer) endowed with anti-apoptotic roles and of globoside Gb3 related to a higher expression of the multidrug resistance gene MDR1. In light of this evidence, the employment of chemical or genetic approaches specifically targeting sphingolipid dysregulations appears a promising tool for the improvement of current chemotherapy efficacy.

The ganglioside G(D2) induces the constitutive activation of c-Met in MDA-MB-231 breast cancer cells expressing the G(D3) synthase

We have recently established and characterized cellular clones deriving from MDA-MB-231 breast cancer cells that express the human G(D3) synthase (GD3S), the enzyme that controls the biosynthesis of b- and c-series gangliosides. The GD3S positive clones show a proliferative phenotype in the absence of serum or growth factors and an increased tumor growth in severe immunodeficient mice. This phenotype results from the constitutive activation of the receptor tyrosine kinase c-Met in spite of the absence of ligand and subsequent activation of mitogen-activated protein kinase/extracellular signal-regulated kinase and phosphoinositide 3-kinase/Akt pathways. Here, we show by mass spectrometry analysis of total glycosphingolipids that G(D3) and G(D2) are the main gangliosides expressed by the GD3S positive clones. Moreover, G(D2) colocalized with c-Met at the plasma membrane and small interfering RNA silencing of the G(M2)/G(D2) synthase efficiently reduced the expression of G(D2) as well as c-Met phosphorylation and reversed the proliferative phenotype. Competition assays using anti-G(D2) monoclonal antibodies also inhibit proliferation and c-Met phosphorylation of GD3S positive clones in serum-free conditions. Altogether, these results demonstrate the involvement of the disialoganglioside G(D2) in MDA-MB-231 cell proliferation via the constitutive activation of c-Met. The accumulation of G(D2) in c-Met expressing cells could therefore reinforce the tumorigenicity and aggressiveness of breast cancer tumors.

Functional activation of Src family kinase yes protein is essential for the enhanced malignant properties of human melanoma cells expressing ganglioside GD3

The possible roles of Src family kinases in the enhanced malignant properties of melanomas related to GD3 expression were analyzed. Among Src family kinases only Yes, not Fyn or Src, was functionally involved in the increased cell proliferation and invasion of GD3-expressing transfectant cells (GD3+). Yes was located upstream of p130Cas and paxillin and at an equivalent level to focal adhesion kinase. Yes underwent autophosphorylation even before serum treatment and showed stronger kinase activity in GD3+ cells than in GD3- cells following serum treatment. Coimmunoprecipitation experiments revealed that Yes bound to focal adhesion kinase or p130Cas more strongly in GD3+ cells than in GD3- cells. As a possible mechanism for the enhancing effects of GD3 on cellular phenotypes, it was shown that majority of Yes was localized in glycolipid-enriched microdomain/rafts in GD3+ cells even before serum treatment, whereas it was scarcely detected in glycolipid-enriched microdomain/rafts in GD3- cells. An in vitro kinase assay of Yes revealed that coexistence of GD3 with Yes in membranous environments enhances the kinase activity of GD3- cell-derived Yes toward enolase, p125, and Yes itself. Knockdown of GD3 synthase resulted in the alleviation of tumor phenotypes and reduced activation levels of Yes. Taken together, these results suggest a role of GD3 in the regulation of Src family kinases.

Highly sensitive localization analysis of gangliosides and sulfatides including structural isomers in mouse cerebellum sections by combination of laser microdissection and hydrophilic interaction liquid chromatography/electrospray ionization mass spectrometry with theoretically expanded multiple reaction monitoring

Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is suitable for analysis of glycosphingolipids such as fragile gangliosides avoiding the use of the sialic acid elimination. However, it was not possible to distinguish the structural isomers such as GD1a and GD1b with reversed-phase LC/ESI-MS by hydrophobic interaction. Here we report an effective method for targeted analysis of theoretically expanded ganglioside molecular species including structural isomers by hydrophilic interaction liquid chromatography (HILIC)/ESI-MS with multiple reaction monitoring (MRM). As a result of MRM analysis of glycosphingolipid mixtures from porcine brain, each of the lipid classes was detected within 25 min in the following order: sulfatides > GM3 > GM2 > GM1 > GD3 > GD1a > GD2 > GD1b > GT1a > GT1b > GQ1b. For the advanced application, localization analysis of postnatal day 15 (P15) mouse cerebellum layered structures was carried out by combination of MRM and laser microdissection (LMD). As a result, GM3, GD1a, GT1b and GQ1b were abundantly detected in the molecular and granular layers, whereas GM1 was widely presented in each layered structure. These gangliosides were mainly composed of d18:1-18:0 and d18:1-20:0, but GM3 was d18:1-16:0 and d18:1-20:0. Meanwhile, sulfatide molecular species were mostly localized in the myelinated fibers and scarcely found in the molecular layer. These results suggested that our method is suitable to detect a variety of ganglioside classes and sulfatides with high sensitivity at the molecular species level and effective for localization analysis of these glycosphingolipids from mouse brain sections.

GD₃ synthase expression enhances proliferation and tumor growth of MDA-MB-231 breast cancer cells through c-Met activation

The disialoganglioside G(D3) is overexpressed in ∼50% of invasive ductal breast carcinoma, and the G(D3) synthase gene (ST8SIA1) displays higher expression among estrogen receptor-negative breast cancer tumors, associated with a decreased overall survival of breast cancer patients. However, no relationship between ganglioside expression and breast cancer development and aggressiveness has been reported. We have previously shown that overexpression of G(D3) synthase induces the accumulation of b- and c-series gangliosides (G(D3), G(D2), and G(T3)) at the cell surface of MDA-MB-231 breast cancer cells together with the acquisition of a proliferative phenotype in the absence of serum. Here, we show that phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase/extracellular signal-regulated kinase pathways are constitutively activated in G(D3) synthase-expressing cells. Analysis of phosphorylation of tyrosine kinase receptors shows a specific c-Met constitutive activation in G(D3) synthase-expressing cells, in the absence of its ligand, hepatocyte growth factor/scatter factor. In addition, inhibition of c-Met or downstream signaling pathways reverses the proliferative phenotype. We also show that G(D3) synthase expression enhances tumor growth in severe combined immunodeficient mice. Finally, a higher expression of ST8SIA1 and MET in the basal subtype of human breast tumors are observed. Altogether, our results show that G(D3) synthase expression is sufficient to enhance the tumorigenicity of MDA-MB-231 breast cancer cells through a ganglioside-dependent activation of the c-Met receptor.

GD3 synthase overexpression enhances proliferation and migration of MDA-MB-231 breast cancer cells

The disialoganglioside G(D3) is an oncofetal marker of a variety of human tumors including melanoma and neuroblastoma, playing a key role in tumor progression. G(D3) and 9-O-acetyl-G(D3) are overexpressed in approximately 50% of invasive ductal breast carcinoma, but no relationship has been established between disialoganglioside expression and breast cancer progression. In order to determine the effect of G(D3) expression on breast cancer development, we analyzed the biosynthesis of gangliosides in several breast epithelial cell lines including MDA-MB-231, MCF-7, BT-20, T47-D, and MCF10A, by immunocytochemistry, flow cytometry, and real-time PCR. Our results show that, in comparison to tumors, cultured breast cancer cells express a limited pattern of gangliosides. Disialogangliosides were not detected in any cell line and G(M3) was only observed at the cell surface of MDA-MB-231 cells. To evaluate the influence of G(D3) in breast cancer cell behavior, we established and characterized MDA-MB-231 cells overexpressing G(D3) synthase. We show that G(D3) synthase expressing cells accumulate G(D3), G(D2), and G(T3) at the cell surface. Moreover, G(D3) synthase overexpression bypasses the need of serum for cell growth and increases cell migration. This suggests that G(D3) synthase overexpression may contribute to increasing the malignant properties of breast cancer cells.

GD3, an overexpressed tumor-derived ganglioside, mediates the apoptosis of activated but not resting T cells

We previously elucidated an important role for gangliosides in renal cell carcinoma-mediated T lymphocyte apoptosis, although the mechanism by which they mediated lymphocyte death remained unclear. Here, we show that when added in purified form, GD3 is internalized by activated T cells, initiating a series of proapoptotic events, including the induction of reactive oxygen species (ROS), an enhancement of p53 and Bax accumulation, an increase in mitochondrial permeability, cytochrome c release, and the activation of caspase-9. GD3-induced apoptosis of activated T cells was dose dependent and inhibitable by pretreating the lymphocytes with N-acetylcysteine, cyclosporin A, or bongkrekic acid, emphasizing the essential role of ROS and mitochondrial permeability to the process. Ganglioside-induced T-cell killing was associated with the caspase-dependent degradation of nuclear factor-kappaB-inducible, antiapoptotic proteins, including RelA; this suggests that their loss is initiated only after the cascade is activated and that their disappearance amplifies but not triggers GD3 susceptibility. Resting T cells did not internalize appreciable levels of GD3 and did not undergo any of the proapoptotic changes that characterize activated T lymphocytes exposed to the ganglioside. RelA overexpression endows Jurkat cells with resistance to GD3-mediated apoptosis, verifying the role of the intact transcription factor in mediating protection from the ganglioside.

Gene expression of ceramide kinase, galactosyl ceramide synthase and ganglioside GD3 synthase is associated with prognosis in breast cancer

PURPOSE

Sphingolipids are bioactive lipids implicated in apoptosis, cell survival and proliferation. We analyzed the prognostic value of enzymes from sphingolipid metabolism in breast cancer.

METHODS

Differences in expression of ceramide galactosyl transferase (UGT8), ceramide kinase (CERK), and Ganglioside GD3-Synthase (ST8SIA1) in breast cancer cells were investigated by using microarray data of 1,581 tumor samples.

RESULTS

UGT8, CERK, and ST8SIA1 were associated with poor pathohistological grading (P < 0.001). High CERK expression was correlated with ErbB2 status (P = 0.006). Among ER positive breast cancers a significant worse prognosis for patients with tumors showing low ST8SIA1 and UGT8 expression was observed. In the ER negative subgroup those samples with high CERK expression displayed a worse prognosis. In a multivariate analysis only ST8SIA1 and tumor size remained significant.

CONCLUSIONS

Our experiments reveal that expression of enzymes from the sphingolipid metabolism has prognostic implications in breast cancer.

Non-specific effects of siRNAs on tumor cells with implications on therapeutic applicability using RNA interference

Elimination of protein expression using RNA interference (RNAi) significantly improves the understanding of gene function and represents a promising technique for the treatment of diseases such as cancer and neurological disorders. Accumulating evidence suggests the so-called interferon-independent non-specific gene silencing of short interfering RNA (siRNA); however, its biological and functional cellular consequences are largely unidentified. We therefore analyzed the effects of different nonsense siRNAs on characteristic bio-parameters such as cell viability, proliferation, cell cycle distribution, apoptosis, and migration of tumor cells. All analyzed cellular aspects have been observed to be significantly affected by the presence of siRNA in an interferon-independent manner: viability, mitosis, and motility were significantly diminished and programmed cell death was significantly elevated. Moreover, all cell cycle stages (G0/G1-, G2/M-, and S-phase) were moderately shifted. Together, these results support the hypothesis that siRNA, due to sequence-specific cellular consequences, modulate bio-functionality independent of the target sequence. This phenomenon affects the design of siRNA experiments for future in vitro but also for in vivo tests as well as for potential therapeutic and preventive strategies. Moreover, monitoring interferon response after transfection of siRNAs is necessary but not sufficient to exclude potential off-target effects in non-diseased cells.